1. Field of the Invention
The present invention relates to a mobile communication system supporting carrier aggregation. More specifically, the present invention relates to a method and apparatus for reporting Power Headroom (PH) of a User Equipment (UE) per carrier efficiently in a mobile communication system supporting carrier aggregation.
2. Description of the Related Art
Mobile communication systems developed to provide subscribers with voice communication services on the move. With the rapid advance of technology, mobile communication systems have evolved to support high speed data communication services as well as standard voice communication services.
Recently, Long Term Evolution (LTE) is under development as the next generation mobile communication system of the 3rd Generation Partnership Project (3GPP). The LTE system is a technology for realizing high-speed packet-based communication at about 100 Mbps. A discussion is being held on several schemes for LTE, including one scheme for reducing the number of nodes located in a communication path by simplifying a configuration of the network, and another scheme for maximally approximating wireless protocols to wireless channels.
Unlike voice services, resources for data services are allocated according to the data amount to be transmitted and channel condition. Accordingly, in a wireless communication system such as a cellular communication system, a scheduler manages resources according to the resource amount, channel condition, and data amount. This is also the case in the LTE system, in which the scheduler located in the base station manages and allocates the radio resource.
Recently, LTE-Advanced (LTE-A) is actively being discussed as an evolution of LTE with new techniques to increase data rates. Carrier aggregation is one of the representative techniques that are newly adopted in LTE-A. Unlike the data communication of the related art in which a User Equipment (UE) uses a single uplink carrier and a single downlink carrier, carrier aggregation enables the UE to use multiple uplink and/or downlink carriers. Since the uplink transmission power determination algorithm is designed for the UE operating with one uplink carrier and one downlink carrier, it is difficult to apply the transmission power determination process for uplink transmission power determination of the UE supporting carrier aggregation. There is a need to define a procedure and method for reporting Power Headroom (PH) of the UE supporting carrier aggregation.